In WO 2007/017879 A2 a cardiac resynchronization therapy (CRT) is disclosed, in which pacer electrodes are implanted in cardiac chambers and vessels. The idea of CRT is to improve the cardiac output by pacing the right and the left heart chambers in an optimal way by the pacer electrodes. In order to find the optimal position and adaptation of the pacer electrodes, e.g. a position and an adaptation leading to a synchronized movement of the right and left heart chambers, several adaptations and positions of the electric pacer electrodes have to be tried and for each combination of adaptation and position of the pacer electrodes the degree of cardiac synchrony, in particular of synchrony of the left and right heart chambers, has to be determined. Since the heart tissue and the heart vessels are not visible in an X-ray imaging device, which is generally present during CRT for tracking the position of the pacer electrodes, an additional imaging device is required for determining the above mentioned functional property of the heart, i.e. the degree of cardiac synchrony. The WO 2007/017879 A2 discloses an ultrasound imaging device as this additional imaging device. The wall of the heart is visible in the ultrasound imaging device and wall motion dynamics can be determined from the images of the ultrasound imaging device for determining the degree of cardiac synchrony. The need for an additional imaging device to image the heart during CRT makes the system complex and more expensive.
It is therefore an object of the present invention to provide a system, a method and a computer program for determining a functional property of a moving object, without the need for direct imaging of the object itself.
In a first aspect of the present invention a system for determining a functional property of a moving object is presented, wherein the system comprises:                a tag contactable to the object such that the tag follows the movement of the object,        a movement determination device for determining the movement of the tag, and        a functional property determination device for determining a functional property of the object from the determined movement of the tag.        
The invention is based on the idea that, since the system only needs the ability to determine the movement of the tag, the movement of the object itself does not need to be directly interrogated by the movement determination device. The tag can be selected such that the movement of the tag can easily be determined by the movement determination device. Since the tag is contactable to the object such that the tag follows the movement of the object, the determined movement of the tag is correlated to the movement of the object and, thus, the functional property determination device can determine a functional property of the object from the determined, in particular, quantified, movement of the tag. Therefore, the system in accordance with the present invention allows for determination of a functional property of the object without the need for determining the movement of the object directly, in particular without the need for direct imaging of the object in question. A functional property of the object can therefore be determined, even if the movement of the object itself cannot directly be determined, in particular even if the object itself cannot be visualized by an imaging device.
The movement of the tag is preferentially represented by a motion vector or a motion vector field and the functional property is preferentially determined from the motion vector or the motion vector field, respectively.
The object is preferentially a moving organ like a human heart, wherein the tag is contactable to the moving organ such that the movement follows the movement of the object. In particular, the object is preferentially a heart muscle and/or a heart chamber and further preferred a moving wall of a heart muscle or a heart chamber.
In general, the determined movement of the tag is caused by a movement of the object being a real absolute or relative movement of the whole object or of at least a part of the object, but the determined movement can also be a zero movement, i.e. the determination device could also determine that the tag is not moving at all.
The tag is selected such that the movement of the tag can be determined by the movement determination device. The movement determination device includes preferentially an X-ray imaging system, for example, an X-ray fluoroscopy system being, for example, a simple X-ray projection imaging system, a computed tomography imaging system or an X-ray C-arm system. In particular, if the movement determination device includes an X-ray imaging system, the tag is selected such that it can be detected by X-rays, i.e. in this case the tag is preferentially a highly X-ray attenuating element, in particular catheters, wires, electrodes or leads comprising metallic elements. The motion determination device preferentially tracks the tag temporally and spatially in order to determine the movement of the tag.
In a preferred embodiment, the system comprises a plurality of tags, wherein the movement determination device is adapted for determining the movement of several tags and wherein the functional property determination device is adapted for determining one or several functional properties from the determined movements of the tags. If the system comprises several tags, the tags can represent more accurately the movement of the object and, thus, one or several functional properties of the object can be determined more accurately, in particular if different parts of the object move differently.
The tag can be attached to the object and/or it can abut the object such that there is a continuous contact between the object and the tag at least during a predetermined time interval. Preferentially, the tags are implanted in the object.
The functional property determination device can be adapted for determining only one functional property or for determining several functional properties from the determined movement of the tag or from the determined movements of the tags.
It is further preferred, that the movement determination device is adapted for determining a temporal, i.e. time-dependent, image of the tag and for determining the movement of the tag from the temporal image. This image-based determination of the movement of the tag, i.e. the tracking of the tag, can be performed by any appropriate method, for example, snake-based, vessel-filter based, correlation-based, template-based or the like.
In a preferred embodiment, the functional property determination device is adapted for determining a movement of the object from the determined movement of the tag and for determining the functional property of the object from the determined movement of the object. Since the functional property of the object, which is determined by the functional property determination device, depends on the movement of the object, the determination of the functional property directly from the determined movement of the object further improves the degree of accuracy of the determined functional property.
It is preferred that the moving object is a first object within a second object, wherein the tag is insertable into the second object for contacting the tag to the first object such that it follows the movement of the first object. This allows determining of a functional property of a moving object, even if the moving object is located within a second object. The first object is, in particular, a human heart located within a patient being the second object. In particular, this allows determining a functional property of a human organ, like a human heart.
It is further preferred that the moving object is a moving heart, wherein at least one first tag is contactable to the right chamber of the heart, wherein at least one second tag is contactable to the left chamber of the heart, wherein the movement determination device is adapted for determining a movement of the at least one first tag and of the at least one second tag. This allows determining a functional property of the heart, which is correlated with the movement of the right chamber and the left chamber of the heart, in particular cardiac synchrony and/or cardiac output. It is further preferred that the system comprises at least one third tag, which is contactable to an atrium of a human heart, in particular to the right atrium of a human heart, wherein the movement determination device is adapted for determining a movement of the at least one third tag. This allows determining a functional property of the heart, in particular the cardiac synchrony and/or the cardiac output, from a movement of the at least one third tag, and in particular, in addition, from the movement of the at least one first tag and the at least one second tag.
It is further preferred that the functional property determination device is adapted for determining the movement of the right chamber of the heart from the at least one first tag and the movement of the left chamber of the heart from the at least one second tag. Since the functional property determined by the functional property determination device is correlated with the movement of the heart, the determined movements of the right chamber and the left chamber of the heart can be used for determining the function& property of the heart more accurately.
It is preferred that the functional property determination device is adapted for determining a degree of synchrony between the movement of the right chamber and the left chamber of the heart from the determined movement of the at least one first tag and the at least one second tag and, in particular, from a determined movement of at least one third tag contacted to an atrium of the heart. The degree of synchrony can be used in a CRT. Thus, the determination of the degree of synchrony allows controlling an adaptation and/or a positioning of pacer electrodes during a CRT such that the degree of synchrony is maximized. This is preferentially performed by firstly determining the movement of the heart chambers from the determined movement of the tags and secondly by determining the degree of synchrony from the determined movement of the heart chambers. But, it is also preferred that the degree of synchrony is determined directly from the determined movement of the tags.
It is further preferred that the functional property determination device is adapted for determining a degree of cardiac synchrony including the synchrony between the movement of the right chamber and the left chamber of the heart from the determined movement of the at least one first tag, of the at least one second tag and of at least one third tag, which is contacted to an atrium of the heart, in particular to the right atrium of the heart. Also this degree of cardiac synchrony can be used in a CRT.
It is further preferred that the functional property determination device is adapted for determining a cardiac output from the determined movement of the at least one first tag and the at least one second tag and, in particular, from a determined movement of at least one third tag contacted to an atrium of the heart. Also the determined cardiac output can be used for adapting and positioning pacer electrodes in a CRT such that the properties and positions of the pacer electrodes are optimized, i.e., in this case, that the cardiac output is optimized.
Also the cardiac output can be determined by firstly determining the movement of the heart chambers from the movement of the tags and by secondly determining the cardiac output from the determined movement of the heart chambers. In another embodiment, the cardiac output can be determined from the degree of synchrony of the left and the right heart chambers.
It is further preferred that the system comprises a movement influencing element for influencing the movement of the object. Movement influencing elements are separate elements and/or at least one tag is a movement influencing element. Preferentially, the moving influencing element is a pacing element for pacing a heart, in particular the above mentioned pacer electrode.
Preferentially, the system further comprises an adaptation device for adapting the moving influencing element such that the determined functional property of the object is maximized. For example, if the moving influencing element is a pacing element for pacing a heart, the adaptation device preferentially modifies the amperage and/or the frequency of a current for pacing a human heart such that the determined functional property, which is preferentially a degree of cardiac synchrony, in particular of synchrony of the left and right heart chambers, in particular of the left and right heart chamber contractions, and/or a cardiac output, is maximized.
It is further preferred that the system further comprises a positioning device for positioning the moving influencing element such that the determined functional property of the object is maximized. If the moving influencing element is a pacing element for pacing a human heart, the pacing elements are preferentially positioned such that the determined functional property, which is preferentially a degree of cardiac synchrony, in particular of synchrony of the left and right heart chambers, in particular of the left and right heart chamber contractions, and/or the cardiac output, is maximized.
In a preferred embodiment, the movement influencing element is changeable at least between a first influencing condition and a second influencing condition, wherein the movement determination device and the movement influencing elements are controllable such that a first movement of the tag is determined if the movement influencing element is in the first influencing condition and that a second movement of the tag is determined if the movement influencing element is in the second influencing condition, and wherein the functional property determination device is controllable such that the functional property is determined at least twice, one time from the first movement of the tag and another time from the second movement of the tag, in order to determine the influence of the movement influencing element on the functional property of the object. Preferentially, the first influencing condition is a condition, in which the movement influencing element is activated, and the second influencing condition is preferentially a condition, in which the movement influencing element is deactivated. This allows determining the influence of different conditions of the moving influencing element on the functional property of the object.
It is further preferred that the system comprises a visualization unit for visualizing the determined functional property of the object simultaneously with a visualization of the tag. This gives a user a visualization of a correlation between a position of the tag and the determined functional property. It is preferred that different movements of the tag for example, in different directions or in different velocity ranges, are indicated by different colors.
In a further aspect of the present invention a method for determining a functional property of a moving object is presented, wherein the method comprises:                providing a tag contacted to the object such that the tag follows the movement of the object,        determining the movement of the tag,        determining a functional property from the determined movement of the tag.        
In further aspect of the present invention a computer program for determining a functional property of a moving object is determined, wherein the computer program comprises program code means for causing a system as described to carry out the steps of the method as described, when the computer program is run on a computer controlling the system.
It shall be understood that the system, the method and the computer program have similar and/or identical preferred embodiments as defined in the dependent claims. it shall be understood that preferred embodiments of the invention can also be any combination of the dependent claims.